Process of producing tungsten powder.



UNITED STATES PATENT OFFICE.

ROBERT RAFN, OF PORSGRUND, NORWAY, ASSIGNOR TO GENERAL ELECTRIC COMPANY,OF SCHENECTADY, NEW YORK, A CORPORATION.

PROCESS FOR PRODUCING TUNGSTEN POWDER.

No Drawing.

To all whom it may concern:

Be it known that I, ROBERT RAFN, subject of the King of Norway, andresiding at Porsgrund, Norway, have invented certain new and usefulImprovements in Processes for Producing Tungsten Powder, of which thefollowing is a specification.

It is known that when tungsten-trioxid is reduced by means of hydrogenas a rule a crystalline metal results. It is only by taking specialprecautionary measures that an amorphous tungsten, suitable for makingfilaments can be obtained by this method. In order to obtain ahomogenous product, extraordinary skill in carrying out the process isrequired and close observation of a large number of details.

Exhaustive experiments have shown that an excellent initial material,suitable for making up into tungsten filaments, can be obtained byreducing the tungsten-trioxid to metal in two stages. First ammonia gasis passed over the tri-oxid, with the furnace at a dull red heat. Bythis means the so-called blue tungsten-oxid is obtained. Then thetemperature is raised rapidly to cherry red and simultaneously hydrogenis introduced into the furnace in place of the ammonia gas. Theresulting product is a tungsten powder of remarkable fineness.

Exactly what takes place when this process as described is carried outhas not been actually determined. The eculiar behavior can be perhapsexplained y the formation Specification of Letters Patent.

,at a certain temperature and completely re- Patented Mar. 2, 1915.

Application filed September 20, 1912. Serial No. 721,443.

of an intermediate product containing hydrogen or nitrogen. It is,however, also ossible that when the process is carried out in the mannerdescribed the appearance of a lower oxid is prevented, which generallyhas a crystalline form.

What I claim is:

1. A process for producin metallic tungsten powder which is suita le formaking filaments, consisting of heating tungstentrioxid at a dull redheat in ammonia gas to produce blue tungsten-oxid and then heating saidblue oxid in an atmosphere of hydrogen at a higher temperature.

2. A process for producing metallic tungsten powder, consisting ofreducing tungsten-trioxid to blue tungsten-oxid by heating it in ammoniagas, then substituting an atmosphere of hydrogen for the ammonia gas andrapidly raisin the temperature of the blue oxid to reduce it to metal.

3. A process for producing fine metallic tungsten powder, consisting ofreducing tungsten tri-oxid in the first stage to blue oxid by onereagent, then in the second stage 6O ducing the blue oxid to metal byanother neagent at a higher temperature.

In testimony whereof I aflix my signature in presence of two witnesses.

ROBERT RAFN. Witnesses:

OSCAR Boon, RALPH W. Dox.

It is hereby certified that in Letters Patent No. 1,130,197, grantedMarch 2, 1915,

upon the application of Robert Rafn, of Porsgrund, Norway, for animprovement in Processes for Producing Tungsten Powder, errors appear inthe printed specification requiring correction as follows: Line 59,after the word reagent insert the words at a certain temperature and;line 60, strike out the words at a. certain temperature and; and thatthe said Letters Patent should be read with these corrections thereinthat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 30th day of March, A. D., 1915.

[slant] J. T. NEWTON,

Acting Commissioner of Patents.

